Drivers of residual sediment transport in a stratified estuarine channel

Abstract

The bed stability of an estuary is determined by the net import or export of sediment, which in turn is controlled by multiple processes. Apart from the upstream riverine sediment supply, the net sediment flux is largely controlled by tidal hydrodynamics and the associated sediment exchange with the sea. In general, flood dominance causes landward residual sediment transport (sediment import from the sea), and ebb dominance causes seaward residual sediment export to the sea (Guo et al., 2014). In the New Waterway, The Netherlands, , residual fluxes are mainly associated with upstream and downstream advective transport in the salt wedge and in the fresh water layer, respectively. The associated processes have been well documented (De Nijs et al., 2010; Dronkers, 2017), which result in accumulation of sediment near the tip of the salt wedge (De Nijs et al., 2010). While it is known that mixing between freshwater and saltwater layers plays an important role in the residual salinity flux, little is known however about the exchange of sediment between both layers. We aim to quantify and understand the exchange of sediment across the freshwater-saltwater interface based on field data in a stratified tidal channel.